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"""Taken from multiprocessing.util.Finalize."""
import weakref
from itertools import count
class Finalize(object):
"""Object finalization using weakrefs."""
_count = count().next
_registry = {}
def __init__(self, obj, callback, args=(), kwargs=None,
exitpriority=None):
if obj is not None:
self._weakref = weakref.ref(obj, self)
else:
assert exitpriority is not None
self._callback = callback
self._args = args
self._kwargs = kwargs or {}
self._key = (exitpriority, self._count())
self._registry[self._key] = self
def __call__(self, wr=None):
"""Run the callback unless it has already been called or
cancelled."""
try:
self._registry.pop(self._key)
except KeyError:
pass
else:
try:
return self._callback(*self._args, **self._kwargs)
finally:
self._reset()
def _reset(self):
self._weakref = self._callback = self._args = \
self._kwargs = self._key = None
def cancel(self):
"""Cancel finalization of the object."""
try:
self._registry.pop(self._key)
except KeyError:
pass
else:
self._reset()
def still_active(self):
self._key in self._registry
def __repr__(self):
try:
obj = self._weakref()
except (AttributeError, TypeError):
return "<Finalize: (dead)>"
if obj is None:
return
x = '<Finalize object, callback=%s' % \
getattr(self._callback, '__name__', self._callback)
if self._args:
x += ', args=%r' % (self._args, )
if self._kwargs:
x += ', kwargs=%r' % (self._kwargs, )
if self._key[0] is not None:
x += ', exitprority=%r' % (self._key[0], )
return x + '>'
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